Abstract: A diffuser for a centrifugal compressor has an annular array of vanes which are movable to vary the configuration of the diffusing passages between the vanes. Each vane includes a first leaf pivoted adjacent the leading edge of the vane and a second leaf pivoted on the first leaf. These leaves have slots extending chordwise of the vanes which are engaged by pins extending from an actuating ring rotatable about the axis of the diffuser. The slots in the two leaves are at an angle to each other so that when the ring is rotated and the pins move chordwise of the vanes in the leaves, the angle of the first leaf to the radial direction is changed and also the second leaf is moved relative to the first leaf to vary the width of the passage in addition to such variation as results from the change in the angle of the first leaf.